A curve that can be obtained from the intersection of a right circular cone and a plane.
When these curves are represented in a plane, they are called algebraic curves, which refers to the locus of points in a plane for which the distances to a point (focus) divided by the distances to a line (directrix) on this plane is a constant (eccentricity).
Therefore, a conic section is the set of points P on the directrix d. The number k is called the eccentricity of the conic section.
Algebraic curves, commonly referred to as conic sections, are circles, ellipses, parabolas and hyperbolas.
The adjective conical describes that which has the shape of a cone: conical surface, conical base, etc.